YANG Groupings for Transmission Control Protocol (TCP) Configuration
draft-scharf-tcpm-yang-tcp-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Michael Scharf , Vishal Murgai | ||
| Last updated | 2019-07-07 (Latest revision 2019-02-24) | ||
| Replaced by | draft-ietf-tcpm-yang-tcp, draft-ietf-tcpm-yang-tcp, draft-ietf-tcpm-yang-tcp | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-scharf-tcpm-yang-tcp-02
TCPM M. Scharf
Internet-Draft Hochschule Esslingen
Intended status: Standards Track V. Murgai
Expires: January 8, 2020 Cisco Systems Inc
July 7, 2019
YANG Groupings for Transmission Control Protocol (TCP) Configuration
draft-scharf-tcpm-yang-tcp-02
Abstract
This document specifies a YANG model for TCP on devices that are
configured by network management protocols. The YANG model defines
groupings for fundamental parameters that can be modified in many TCP
implementations. The model extends a base model for TCP clients and
servers [I-D.ietf-netconf-tcp-client-server].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 8, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Scharf & Murgai Expires January 8, 2020 [Page 1]
Internet-Draft TCP Configuration July 2019
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Model Overview . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Modeling Scope . . . . . . . . . . . . . . . . . . . . . 3
3.2. Basic TCP Configuration Parameters . . . . . . . . . . . 5
3.3. Model Design . . . . . . . . . . . . . . . . . . . . . . 6
3.4. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 7
4. TCP Configuration YANG Model . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 10
Appendix B. Changes compared to previous versions . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The Transmission Control Protocol (TCP) [RFC0793] is used by many
applications in the Internet, including control and management
protocols. Therefore, TCP is implemented on network elements that
can be configured via network management protocols such as NETCONF
[RFC6241] or RESTCONF [RFC8040]. This document specifies a YANG
model [RFC6020][RFC7950] for configuring TCP on network elements that
support YANG data models. This document extends a base model for TCP
clients and servers [I-D.ietf-netconf-tcp-client-server]. The model
focuses on fundamental and standard TCP functions that are widely
implemented. The model can be augmented to address more advanced or
implementation-specific TCP features. Operational state and
statistics are outside the scope of this memo.
Many protocol stacks on Internet hosts use other methods to configure
TCP, such as operating system configuration or policies. Many TCP/IP
stacks cannot be configured by network management protocols such as
NETCONF or RESTCONF and they do not use YANG data models. Yet, such
TCP implementations often also have means to configure the parameters
listed in this document. All parameters defined in this document are
optional.
This specification is orthogonal to a Management Information Base
(MIB) for the Transmission Control Protocol (TCP) that has been
standardized [RFC4022]. A MIB providing extended statistics for TCP
Scharf & Murgai Expires January 8, 2020 [Page 2]
Internet-Draft TCP Configuration July 2019
is also available [RFC4898], and there are also MIBs for UDP
[RFC4113] and SCTP [RFC3873]. It is possible to translate a MIB into
a YANG model, for instance using the translation described in
[RFC6643]. However, this approach is not used in this document, as
such a translated model would not be up-to-date.
There are also other related YANG models. Examples are:
o Application protocol models may include TCP parameters, for
example in case of BGP [I-D.ietf-idr-bgp-model].
o TCP header attributes are modeled in other models, such as
[I-D.ietf-netmod-acl-model].
o TCP-related configuration of a NAT is defined in
[I-D.ietf-opsawg-nat-yang].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Model Overview
3.1. Modeling Scope
TCP is implemented on many different system architectures. As a
result, there are may different and often implementation-specific
ways to configure parameters of the TCP protocol engine. In
addition, in many TCP/IP stacks configuration exists for different
scopes:
o Global configuration: Many TCP implementations have configuration
parameters that affect all TCP connections. Typical examples
include the enabling or disabling optional protocol features.
o Interface configuration: It can be useful to use different TCP
parameters on different interfaces, e.g., different device ports
or IP interfaces. In that case, TCP parameters can be part of the
interface configuration. Typical examples are the Maximum Segment
Size (MSS) or configuration related to hardware offloading.
o Connection parameters: Many implementations have means to
influence the behavior of each TCP connection, e.g., on the
programming interface used by applications. A typical example are
Scharf & Murgai Expires January 8, 2020 [Page 3]
Internet-Draft TCP Configuration July 2019
socket options in the socket API, such as disabling the Nagle
algorithm by TCP_NODELAY. In an application uses such an
interface, it is possible that the configuration of the
application or application protocol includes TCP-related
parameters. An example is the YANG model for BGP configuration
[I-D.ietf-idr-bgp-model].
o Policies: Setting of TCP parameters can also be part of system
policies, templates, or profiles. An example would be the
preferences defined in the TAPS interface
[I-D.ietf-taps-interface].
There is no ground truth for setting certain TCP parameters, and
traditionally different implementation have used different modeling
approaches. For instance, one implementation may define a given
configuration parameter globally, while another one uses per-
interface settings, and both approaches work well for the
corresponding use cases. Also, different systems may use different
default values.
In addition to configuration of the TCP protocol engine, a TCP
implementation typically also offers access to operational state and
statistics. This includes amongst others:
o Statistics: Counters for the number of active/passive opens, sent
and received segments, errors, and possibly other detailed
debugging information
o TCP connection table: Access to status information for all TCP
connections
o TCP listener table: Tnformation about all TCP listening endpoints
This document focuses solely on modeling basic TCP configuration
state. Operational state (see [RFC8342]) is outside the scope of
this specification.
The YANG model defined in this document extends a base model for TCP
clients and servers [I-D.ietf-netconf-tcp-client-server]. Similar to
the base model, this specification only defines YANG groupings. This
allows reuse of these groupings in different YANG data models. It is
intended that these groupings will be used either standalone or for
TCP-based protocols as part of a stack of protocol-specific
configuration models.
Scharf & Murgai Expires January 8, 2020 [Page 4]
Internet-Draft TCP Configuration July 2019
3.2. Basic TCP Configuration Parameters
There are a number of basic system parameters that are configurable
on many TCP implementations, even if not all TCP implementations may
indeed have exactly all these settings. Also, the syntax, semantics
and scope (e.g., global or interface-specific) can be different in
different system architectures.
The following list of fundamental parameters considers both TCP
implementations on hosts and on routers:
o Keepalives (see also [I-D.ietf-netconf-tcp-client-server])
* Idle-time (in seconds): integer
* Probe-interval (in seconds): integer
* Max-probes: integer
o Maximum MSS (in byte): integer
o FIN timeout (in seconds): integer
o SACK (disable/enable): boolean
o Timestamps (disable/enable): boolean
o Path MTU Discovery (disable/enable): boolean
o ECN
* Enabling (disable/passive/active): enumeration
Some other parameters are also common but not ubiquitously supported,
or modeled in very different ways. Therefore, the following
attributes are not considered in this document:
o Delayed ACK timeout (in ms)
o Initial RTO value (in ms)
o Maximum number of retransmissions
o Window scaling
o Maximum number of connections
Scharf & Murgai Expires January 8, 2020 [Page 5]
Internet-Draft TCP Configuration July 2019
TCP can be implemented in different ways and design choices by the
protocol engine often affect configuration options. In a number of
areas there are major differences between different software
architectures. As a result, there are not many commonalities in the
corresponding configuration parameters:
o Window size: TCP stacks can either store window state variables
(such as the congestion window) in segments or in bytes.
o Buffer sizes: The memory management depends on the operating
system. As the size of buffers can vary over several orders of
magnitude, very different implementations exist. This typically
influences TCP flow control.
o Timers: Timer implementation is another area in which TCP stacks
may differ.
o Congestion control algorithms: Many congestion control algorithms
have configuration parameters, but except for fundamental
properties they often tie into the specific implementation.
This document only models fundamental system parameters that are
configurable on many TCP implementations, and for which the
configuration is reasonably similar.
3.3. Model Design
[[Editor's node: This section requires further work.]]
This document extends the YANG model "ietf-tcp-common" defined in
[I-D.ietf-netconf-tcp-client-server]. The exact modeling is TBD.
The intention is to define YANG groupings for all parameters so that
they can be used in different YANG models.
As an example, enabling the support of Selective Acknowledgements
(SACK) can be modelled as follows:
grouping tcp-sack-grouping {
description "Support of Selective Acknowledgements (SACK)";
leaf sack {
type boolean;
default "true";
description
"Enable support of Selective Acknowledgements (SACK)";
}
}
Scharf & Murgai Expires January 8, 2020 [Page 6]
Internet-Draft TCP Configuration July 2019
A YANG model could then, for instance, import the YANG model "ietf-
tcp-common" as well as the model defined in this document as follows:
...
grouping example-tcp-config {
description "Example TCP stack configuration";
uses tcp-common-grouping;
uses tcp-sack-grouping;
}
...
3.4. Tree Diagram
[[Editor's node: This section will be completed in follow-up versions
of this document.]]
This section provides a tree diagram [RFC8340] for the YANG module
defined in this document.
4. TCP Configuration YANG Model
[[Editor's node: This section is TBD.]]
5. IANA Considerations
[[Editor's node: This section will be completed in follow-up versions
of this document.]]
6. Security Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
Scharf & Murgai Expires January 8, 2020 [Page 7]
Internet-Draft TCP Configuration July 2019
7. References
7.1. Normative References
[I-D.ietf-netconf-tcp-client-server]
Watsen, K. and M. Scharf, "YANG Groupings for TCP Clients
and TCP Servers", draft-ietf-netconf-tcp-client-server-02
(work in progress), July 2019.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
Scharf & Murgai Expires January 8, 2020 [Page 8]
Internet-Draft TCP Configuration July 2019
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
7.2. Informative References
[I-D.ietf-idr-bgp-model]
Jethanandani, M., Patel, K., and S. Hares, "BGP YANG Model
for Service Provider Networks", draft-ietf-idr-bgp-
model-06 (work in progress), June 2019.
[I-D.ietf-netmod-acl-model]
Jethanandani, M., Agarwal, S., Huang, L., and D. Blair,
"Network Access Control List (ACL) YANG Data Model",
draft-ietf-netmod-acl-model-21 (work in progress),
November 2018.
[I-D.ietf-opsawg-nat-yang]
Boucadair, M., Sivakumar, S., Jacquenet, C., Vinapamula,
S., and Q. Wu, "A YANG Module for Network Address
Translation (NAT) and Network Prefix Translation (NPT)",
draft-ietf-opsawg-nat-yang-17 (work in progress),
September 2018.
[I-D.ietf-taps-interface]
Trammell, B., Welzl, M., Enghardt, T., Fairhurst, G.,
Kuehlewind, M., Perkins, C., Tiesel, P., and C. Wood, "An
Abstract Application Layer Interface to Transport
Services", draft-ietf-taps-interface-03 (work in
progress), March 2019.
[RFC3873] Pastor, J. and M. Belinchon, "Stream Control Transmission
Protocol (SCTP) Management Information Base (MIB)",
RFC 3873, DOI 10.17487/RFC3873, September 2004,
<https://www.rfc-editor.org/info/rfc3873>.
Scharf & Murgai Expires January 8, 2020 [Page 9]
Internet-Draft TCP Configuration July 2019
[RFC4022] Raghunarayan, R., Ed., "Management Information Base for
the Transmission Control Protocol (TCP)", RFC 4022,
DOI 10.17487/RFC4022, March 2005,
<https://www.rfc-editor.org/info/rfc4022>.
[RFC4113] Fenner, B. and J. Flick, "Management Information Base for
the User Datagram Protocol (UDP)", RFC 4113,
DOI 10.17487/RFC4113, June 2005,
<https://www.rfc-editor.org/info/rfc4113>.
[RFC4898] Mathis, M., Heffner, J., and R. Raghunarayan, "TCP
Extended Statistics MIB", RFC 4898, DOI 10.17487/RFC4898,
May 2007, <https://www.rfc-editor.org/info/rfc4898>.
[RFC6643] Schoenwaelder, J., "Translation of Structure of Management
Information Version 2 (SMIv2) MIB Modules to YANG
Modules", RFC 6643, DOI 10.17487/RFC6643, July 2012,
<https://www.rfc-editor.org/info/rfc6643>.
Appendix A. Acknowledgements
Michael Scharf is supported by the StandICT.eu project, which is
funded by the European Commission under the Horizon 2020 Programme.
Appendix B. Changes compared to previous versions
Changes compared to draft-scharf-tcpm-yang-tcp-01
o Alignment with [I-D.ietf-netconf-tcp-client-server]
o Removing backward-compatibility to the TCP MIB
o Additional co-author
Changes compared to draft-scharf-tcpm-yang-tcp-00
o Editorial improvements
Authors' Addresses
Michael Scharf
Hochschule Esslingen - University of Applied Sciences
Flandernstr. 101
Esslingen 73732
Germany
Email: michael.scharf@hs-esslingen.de
Scharf & Murgai Expires January 8, 2020 [Page 10]
Internet-Draft TCP Configuration July 2019
Vishal Murgai
Cisco Systems Inc
Email: vmurgai@cisco.com
Scharf & Murgai Expires January 8, 2020 [Page 11]